qualify interpretations to avoid clashes

more abstract naming

tuned def. of del and proved preservation of rbt (finally)

tuned order of arguments

split balance into two, clearer etc

got rid of class cmp; added height-size proofs by Daniel Stuewe

avoid name clashes

paint root black after insert and delete

tuned names

Convertd to 3-way comparisons

tuned

added red black trees

--HG--
extra : rebase_source : 28e43c87d5eb14090fa401987d8131c2067f6ab7